New melamine‐formaldehyde‐ketone polymers: I. Synthesis of reactive solvents of melamine from selected ketones

Reactive solvents of melamine were prepared by reacting ketones with an excess of formaldehyde in the presence of triethylamine catalyst. The ketones used were cyclohexanone, cyclopentanone, acetophenone, benzoylacetone, biacetyl, or ethyl‐methyl ketone. The structures of the resulting reactive solvents were studied by ¹H‐NMR. The best solubility of melamine was observed for the solvent derived from ethyl‐methyl ketone. Preliminary attempts at curing the melamine solutions yielded melamine‐formaldehyde‐ketone polymers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95:1319–1332, 2005     

Hysteresis effect on traps of Si3N4 sensing membranes for pH difference sensitivity

The mechanism of different pH sensitivities on single and stacked layer silicon nitride (Si₃N₄)-electrolyte insulator semiconductor (EIS) structures was investigated for the application of an inorganic ion sensitive field effect transistor (ISFET) and reference field effect transistor (REFET) pair. The capacitance-voltage (C-V) hysteresis effect of the EIS structures was measured. In addition, pH sensitivity was evaluated with different sweep directions and ranges of the substrate bias. Based on the hysteresis results, a pH-dependent trapping effect was found to decrease the pH sensitivity on a single Si₃N₄ sensing membrane EIS structure.     

How Far Are We from Making Metamaterials by Self‐Organization? The Microstructure of Highly Anisotropic Particles with an SRR‐Like Geometry

Metamaterials offer new unusual electromagnetic properties, which have already been demonstrated, and many postulated new functionalities are yet to be realized. Currently, however, metamaterials are mostly limited by narrow band behavior, high losses, and limitation in making genuinely 3D materials. In order to overcome these problems an overlap between metamaterial concepts and materials science is necessary. Engineered self‐organization is presented as a future approach to metamaterial manufacturing. Using directional solidification of eutectics, the first experimental realization of self‐organized particles with a split‐ring resonator‐like cross section is demonstrated. This unusual morphology/microstructure of the eutectic composite has a fractal character. With the use of TEM and XRD the clear influence of the atomic crystal arrangement on the microstructure geometry is presented. The materials obtained present very high anisotropy and can be obtained in large pieces. Metallodielectric structures can be created by etching and filling the space with metal. The next steps in the development of self‐organized materials exhibiting unusual properties are discussed.     

High molecular weight diblock and ABA/ABC triblock copolymers of tert‐butyl (meth)acrylate

AB diblock copolymers were prepared by use of poly(tert‐butyl (meth)acrylate) (PtBA/PtBMA) as monofunctional macroinitiator in atom transfer radical polymerization of various (meth)acrylates (methyl, butyl) in the presence of the CuBr/N, N, N′, N′, N″‐pentamethyldiethylenetriamine catalyst system. Then using the diblock copolymer as macroinitiator with a bromine atom at the chain end, ABC and ABA triblock copolymers containing at least one PtBA or PtBMA segment were synthesized via polymerization of the selected (meth)acrylic monomer. Gel permeation chromatography was applied to determine molecular weights and polydispersity indices. The latter, for block copolymers prepared without deactivator addition, were in the range 1.2‐1.6 with a high degree of polymerization (150‐500). The chemical compositions of the block copolymers were characterized with ¹H nuclear magnetic resonance. The kind of combined segments and their lengths influenced the glass transition temperature (T_g) determined by differential scanning calorimetry. Copyright © 2012 Society of Chemical Industry     

Structural Analysis and Intrinsic Enzyme Mimicking Activities of Ligand-Free PtAg Nanoalloys

Nanozymes are nanomaterials with biocatalytic properties under physiological conditions and are one class of artificial enzymes to overcome the high cost and low stability of natural enzymes. However, surface ligands on nanomaterials will decrease the catalytic activity of the nanozymes by blocking the active sites. To address this limitation, ligand-free PtAg nanoclusters (NCs) are synthesized and applied as nanozymes for various enzyme-mimicking reactions. By taking advantage of the mutual interaction of zeolitic imidazolate frameworks (ZIF-8) and Pt precursors, a good dispersion of PtAg bimetal NCs with a diameter of 1.78 ± 0.1 nm is achieved with ZIF-8 as a template. The incorporation of PtAgNCs in the voids of ZIF-8 is confirmed with structural analysis using the atomic pair-distribution function and powder X-ray diffraction. Importantly, the PtAgNCs present good catalytic activity for various enzyme-mimicking reactions, including peroxidase-/catalase- and oxidase-like reactions. Further, this work compares the catalytic activity between PtAg NCs and PtAg nanoparticles with different compositions and finds that these two nanozymes present a converse dependency of Ag-loading on their activity. This study contributes to the field of nanozymes and presents a potential option to prepare ligand-free bimetal biocatalysts with sizes in the nanocluster regime.     

Ancient Bacterial Class Alphaproteobacteria Cytochrome P450 Monooxygenases Can Be Found in Other Bacterial Species

Cytochrome P450 monooxygenases (CYPs/P450s), heme-thiolate proteins, are well-known players in the generation of chemicals valuable to humans and as a drug target against pathogens. Understanding the evolution of P450s in a bacterial population is gaining momentum. In this study, we report comprehensive analysis of P450s in the ancient group of the bacterial class Alphaproteobacteria. Genome data mining and annotation of P450s in 599 alphaproteobacterial species belonging to 164 genera revealed the presence of P450s in only 241 species belonging to 82 genera that are grouped into 143 P450 families and 214 P450 subfamilies, including 77 new P450 families. Alphaproteobacterial species have the highest average number of P450s compared to Firmicutes species and cyanobacterial species. The lowest percentage of alphaproteobacterial species P450s (2.4%) was found to be part of secondary metabolite biosynthetic gene clusters (BGCs), compared other bacterial species, indicating that during evolution large numbers of P450s became part of BGCs in other bacterial species. Our study identified that some of the P450 families found in alphaproteobacterial species were passed to other bacterial species. This is the first study to report on the identification of CYP125 P450, cholesterol and cholest-4-en-3-one hydroxylase in alphaproteobacterial species (Phenylobacterium zucineum) and to predict cholesterol side-chain oxidation capability (based on homolog proteins) by P. zucineum.     

Effects of Polar Organic Solvent on Separation of Y （edta）^-／Nd （edta）^- Complexes on Polyacrylic Anion Exchangers

The use of polar organic solvents for the separations of rare earth elements ( Ⅲ ) is effective especially for their extensive separations despite the solubility limitations.The study shows that polyaerylate anion exchangers, particularly the weakly basic, gel anion exchanger Ambedite IRA 68,can be applied to the separation of rare earth complexes with EDTA in H20-metthanol and H20-ethanol systems.In most cases the determined distribution coefficients of Ln^3 complexes with EDTA in mixed media like water-methanol on polyacrylate anion exchangers are larger than those in pure water media.     

Determination and Modelling of the Influence of Cooling in the Coil on the Mechanical Properties of Hot Strip Steels with Bainite

The phenomenon of bainite formation in the hot strip mill for unalloyed steels and the influence of the complex cooling process have hardly been dealt with in literature. Only two useful model equations were found, namely according to Suehiro et al. [4] for the determination of the strength parameters R_p0.2 and R_m of annealed bainite, and according to Umemoto et al. [2] for the calculation of the tensile strength R_m of bainite formed during the isothermal holding temperature. These equations could be optimized by structural complements and modification of the coefficients by adjusting them to the own measured values. For building up the necessary data base, experimental methods were developed, involving the use of a computerized deformation dilatometer. The results thus obtained can be applied to the industrial practice.